Question

Suppose a culture containing 2*108 bacteria was exposed to ionizing radiation sufficient to kill 99.99% of the cells. calculate the number of bacteria you expect to survive this treatment.

Answer 1

The culture contains 2*10^8 bacteria before it was exposed to ionizing radiation which kills 99.99% of the bacteria. The number of bacteria left after the radiation would be:

final number= initial number * (100%- radiation kill rate)
final number= 2*10^8  *(100%-99.99%)
final number= 2*10^8  *(0.01%)
final number= 2*10^8  * 10^-6
final number= 2*10^(8-6)
final number= 2*10^2